The company said the natural gas-fueled plant will generate 650 megawatts of power. It's being built in Marshalltown.

The plant is expected to go into operation in spring or summer 2017.

"The MGS project has significant economic development and long-term environmental benefits. We are appreciative and grateful for the overwhelming support demonstrated by the community of Marshalltown for the project. Their unconditional support helped make this project a reality," said Doug Kopp president of Alliant Energy’s Iowa utility in a news release.

The new plant is part of the company's multi-billion dollar plan announced in August 2012.